This application claims the benefit of priority based on Japanese Application No. 2002-042068, filed Feb. 19, 2002, which is incorporated by reference herein in its entirety.
The present invention is generally related to a safety device for rotary printing press, more particularly to a safety device for rotary printing press in which a blanket cylinder and a plate cylinder rotate in contact with each other.
A conventional safety device for rotary printing press is disclosed in Examined Japanese Utility Model Publication (KOKOKU) No. Hei 5-3321. The conventional art disclosed therein is related to the protection of an in-running nip formed by the blanket cylinder and the plate cylinder. The safety device is fitted directly to a frame and is a fixed stationary type. When the cylinders are shifted by a trip means between the state in which the outer circumferential surfaces of cylinders are in contact with each other for printing and the state in which the outer circumferential surfaces of cylinders are kept away from each other to make a paper web travel smoothly, to make the loss of paper lesser at the start of printing, to prevent non-printing portion of the cylinders from oiling at the suspension of printing or to prevent paper rolling in operation at a low speed and so on, if the amount of trip of cylinders get large, a gap between the cylinders and a safety member becomes larger in either the state of the outer circumferential surfaces of cylinders being in contact with each other or the state of the outer circumferential surfaces of cylinders being kept away from each other, there is a risk of pulling a tip of fingers or a sleeve of working clothes and so on.
Furthermore, in recent years, internationalization of standard on xe2x80x9cSafety of Machineryxe2x80x9d has come to its highest. In the printing business circle as well, safety standard on printing machine which meets international standard requirements is under consideration, as shown in xe2x80x9cGraphic technologyxe2x80x94Safety requirements for printing press systemsxe2x80x9d of the Draft International Standard ISO/DIS 12648xe2x80x9d issued by Japan Printing Machinery Manufacturers Association in July 2001, for example. With respect to the protection of an in-running nip, consideration is progressively in the direction that a gap between the outer circumferential surface of the cylinders and a nip guard as a guard member is defined to be less than 6 mm as shown in FIG. 5. But, there is the possibility of failure to meet the requirements.
As described above, in a safety device provided in the in-running nip formed by movable cylinders, there has been the need for a safety device in which even if cylinders move a little larger, a gap between the surfaces of cylinders and the guard member can be maintained to be less than a predetermined value and the function of safety protection is kept properly.
Therefore, it is a primary object of the invention to accomplish the above-mentioned objects.
Namely, a safety device according to the present invention is one provided at the feeding side of an in-running nip formed by a rotary body having the center of the rotation thereof being displaceable in position.
The safety device comprises a guard member movably positioned in the vicinity of an outer circumferential surface of the rotary body and a guard member displacement means positioned between the rotary body and the guard member for making the guard member displace in accordance with the displacement of the center of the rotation of the rotary body, and is characterized by that a gap between the outer circumferential surface of the rotary body and the guard member is set to be substantially constant in spite of the movement or shift of the center of the rotation of the rotary body.
By this constitution, as the gap between the outer circumferential surface of the rotary body and the guard member is kept to be substantially constant in spite of the movement or shift of the center of the rotation of the rotary body, safety protection of the in-running nip has become realized.
Furthermore, a safety device includes a guard member that is normally set to be in the state pushed toward the outer circumferential surface of the rotary body by a forcing means, and the guard member displacement means has a receiving surface for receiving a force of the forcing means, and the receiving surface is set to be displaceable in accordance with the movement or shift of the center of the rotation of the rotary body.
By this constitution, the gap between the outer circumferential surface of the rotary body and the guard member is always kept to be substantially constant.
Still further, a safety device includes a guard member displacement means that rotatably supports the rotary body at the displaced or shifted position and has a bearing device provided movably in angular displacement with respect to a frame and also has a cain mounted on the bearing device, and a working surface of the cam is arranged to be the receiving surface.
By such constitution, the gap between the outer circumferential surface of the rotary body and the guard member is always kept to be substantially constant.
Preferably the guard member displacement means is constituted of a trip means, a bearing means and a cam.
Preferably, in addition, the trip means is composed of a link mechanism in which; a driving source of the link mechanism is an actuator for tripping; a tip of a rod of the actuator is coupled movably in angular displacement to an end portion of one of two arms divaricating at an obtuse angle from a center of a crotch arm by making use of a bracket which supports a head side of the actuator as a cardinal point of angular displacement; and the rotary body as a blanket cylinder is movably shifted to the contact position and non-contact position with respect to a printing cylinder having the center of the rotation thereof being fixed.
By such constitution, the trip of the blanket cylinder is detachably done in accordance with extension and retraction of the rod of the actuator.
Further preferably the tip of the other arm of the crotch arm is coupled movably in angular displacement to one end of a connecting rod, and the other end of the connecting rod is coupled movably in angular displacement to an end of salience of the arm which is fitted to a cap constituting a bearing means.
Still further preferably the cap is fitted integrally and movably in angular displacement to a bearing mechanism which is fitted movably in angular displacement about the center of an opening made in a frame, and the bearing mechanism movably supports a shaft of the blanket cylinder in order for the center of the shaft of the blanket cylinder to eccentrically position by a constant quantity of eccentricity apart from the center of the opening, and the cam is provided with a circular arc circumferential surface having a cam surface arranged to be a little larger in radius than the outer circumferential surface of the blanket cylinder and also to be concentric with the blanket cylinder.
Furthermore preferably a guard means including the guard member further comprises a bracket attached to each of the two frames opposing with each other; a stepped or joggled pins installed in a stepped hole of each of the brackets; an L-shape arm fitted movably in angular displacement to each stepped pin with a snap or retaining ring for a shaft; and the guard member is positioned between the two frames in parallel with the center of the shaft of the blanket and arranged to be a little longer than the length of the outer circumferential surface of the blanket cylinder.
Still further preferably a concave hole for spring is provided in a raised portion of the bracket on the opposite side of the blanket cylinder with the L-shape arm between, and a compression spring being a forcing means is loaded in the concave hole for spring so as to regularly push the guard member toward the blanket cylinder via the L-shape arm, and a stopper is provided in the bracket on the opposite side of the raised portion with the L-shape arm between so as to determine the limit of displacement of the guard member pushed toward the blanket cylinder via the L-shape arm.